This invention relates to sensing and, more particularly, to eye tracking.
Various eye tracking techniques are known including oculometers, such as is disclosed in U.S. Pat. No. 3,462,604. An example of another type of eye tracker, based on the detection of Purkinje images, is disclosed in U.S. Pat. No. 3,712,716. Still another example of a type of eye tracker is disclosed in U.S. Pat. No. 4,561,448, based on electro-oculography. These are examples only as other types of eye trackers are known. These can be used to track one or more axes of the attitude, i.e., the pitch, roll and yaw of the eyeball in its socket. Roll, i.e., eyeball torsions can be neglected and are usually not measured. The translatory position of the eyeball within its socket is also not measured it being assumed stationary with respect thereto.
Various head tracking methods are known including Polhemus Navigation Sciences U.S. Pat. Nos. 3,983,474 and 4,017,858 and like patents such as shown in U.S. Pat. No. 3,917,412 to Stoutmeyer. These are used to measure the attitude, i.e., the pitch, roll and yaw of a pilot""s head within a cockpit of a high performance aircraft. The translatory position of the head within the cockpit is not measured. It is evidently neglected and the center of rotation of the pilo""s head is assumed to be stationary with respect to the aircraft.
It is known to combine the above described head and eye monitoring techniques as shown in U.S. Pat. No. 4,028,725 to Lewis. In that case, the helmet attitude measuring system of Stoutmeyer (U.S. Pat. No. 3,917,412) is combined with an eye angle (yaw) detector such as shown in U.S. Pat. No. 3,724,932 to Cornsweet et al. The line of sight of the eye angle of the observer with respect to his head plus the head angle with respect to the center line of the aircraft are measured to control a servoed mirror in front of the eye to keep it always looking at a fixed point on the display. Translatory head position is not measured with respect to any fixed coordinate system of the aircraft.
A contact-analog headup display disclosed in U.S. Pat. No. 5,072,218 showed symbolic images superimposed at selected points on a pilo""s visual field as the aircraft overflies the earth. The position and attitude of the aircraft with respect to the earth and the attitude of the helmet with respect to the aircraft are monitored in order to convert a plurality of stored earth position signals into helmet coordinates. Selected points on earth, such as flightplan waypoints, viewable through the visor of the headup display by the pilot, have symbolic flags planted thereon by means of the display, i.e., the waypoint symbols remain xe2x80x9cstuckxe2x80x9d on the earth, in the eyes of the pilot, regardless of the attitude of the aircraft and regardless of the attitude of the helmet. Eye attitude is not measured nor is there any measurement of translatory head position with respect to the aircraft.
An object of the present invention is to provide a new eye tracking method and apparatus.
According to a first aspect of the present invention, an eye attitude monitor is combined with a head translatory position monitor in order to relate the eye""s translatory position as well as its attitude to an arbitrarily selected reference coordinate system. Eye attitude can mean up to three axes of rotation (pitch, roll, yaw) about an origin of an eye coordinate system. The eye may be approximately assumed to be fixed in position with respect to the origin of a head coordinate system so that any translations in position of the eye with respect to the head may be neglected. This is a good assumption because the eye shifts its position very little in its socket. Its movements involve mostly xe2x80x9cpitchxe2x80x9d and xe2x80x9cyawxe2x80x9d rotations. xe2x80x9cRollxe2x80x9d (torsions) can be neglected as well, if desired. The assumption that the eye is xe2x80x9cfixedxe2x80x9d in translatory position with respect to the origin of the head coordinate system makes it possible to relate the eye""s translatory position to that of the head""s by a translatory transformation of the respective coordinate systems in a simple way, i.e., involving constants only and not requiring any monitoring of the eye""s translatory position with respect to the translatory position of the head.
In further accord with this first aspect of the present invention, a head attitude monitor is added to relate the attitude of the eye to the arbitrarily selected reference coordinate system.
According to a second aspect of the present invention, the attitude of an eye is sensed with respect to an associated head coordinate system for providing an eye attitude signal, the attitude of the head coordinate system is sensed with respect to an arbitrarily selected first reference coordinate system such as a body, vehicle, or inertial reference coordinate system, and instead of sensing the translatory position of the head with respect to the selected first reference coordinate system it is assumed that the translatory position of the head is approximately fixed with respect to the selected first reference coordinate system and the translatory position of the selected first reference coordinate system is sensed with respect to an arbitrarily selected second reference coordinate system such as an inertial reference coordinate system; a visual axis vector signal is then provided referenced, as desired, to the selected first or second reference coordinate system for providing a control signal. Such may, but need not be for controlling an image according to the visual axis vector signal.
The present invention provides a new way to monitor an eye, i.e., with respect to more than one coordinate system, in order to open up new opportunities for eye-controlled devices including, but not limited to, image displays wherein image artifacts, nonuniform image characteristics and the like may be controlled in a way heretofore not possible or contemplated. See for example the positioning of a nonuniform resolution spot on a display according to a monitored visual axis such as disclosed in copending application U.S. Ser. No. 08/001,736, especially in connection with FIGS. 7(a) through 14 at page 29, line 3 through page 51, line 14 which is hereby incorporated by reference.
These and other objects, features, and advantages of the present invention will become more apparent in light of the detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawing.